Transcriptome analysis of Gracilariopsis lemaneiformis at low temperature

Gracilariopsis lemaneiformis is an economically relevant red macroalga whose cultivation is affected by temperature. This study investigated the molecular mechanism of G. lemaneiformis at low temperature. Transcriptomes were obtained after the algae were treated at 5 °C for 6 and 24 h. Among the total clean reads of the 3 groups, 35,324 unigenes were found, of which 81.22% were annotated in at least 1 database (Nr, Nt, Pfam, KOG/COG, Swiss-Prot, KEGG, and GO). A total of 2674 and 3855 differentially expressed genes were found, respectively, after 6 and 24 h of low-temperature treatment at 5 °C. The results of differentially expressed gene analysis by GO and KEGG enrichments showed that the expression of genes related to many pathways changed at low temperatures, such as glutathione metabolism, biosynthesis of unsaturated fatty acids, alpha-linolenic acid metabolism, base excision repair, and photosynthesis. The expression of key genes involved in unsaturated fatty acid synthesis and basic excision repair pathways was significantly upregulated after 6-h low-temperature treatment; however, the expression of key genes involved in the glutathione synthesis pathway was promoted after 24 h. In addition, the expression of some heat shock proteins expected to play an important role in cold resistance was significantly upregulated under low-temperature stress. In summary, the genes related to stress response were induced, while the genes related to photosynthesis were suppressed, indicating that the growth of G. lemaneiformis was affected.